1. Field
The disclosed embodiments generally relate to tracking systems that use retro-directive arrays. More specifically, the disclosed embodiments relate to the design of a tracking system that uses orthogonal polarizations to facilitate efficient operation of a retro-directive array and associated transmit-receive switches.
2. Related Art
Tracking systems based on phase arrays have been used for many years in military radar applications. Recent technological developments are beginning to make it practical to apply these technologies to consumer applications, for example to track controller device from game console. In contrast to military radar applications, the targets for consumer applications can cooperate to ease the tracking process. However, the only practical frequency band for such applications is in the millimeter-wavelength range, which facilitates fitting a small antenna array with a reasonable number of elements to provide fine beam resolution inside a consumer electronic device.
Unfortunately, the poor performance of complementary metal-oxide-semiconductor (CMOS) circuitry at high frequencies can create a significant power burden, which in turn, can adversely affect the battery life of a portable device. It is therefore important to minimize power consumption to enable such technologies to be deployed in mobile applications. This can be done in part by employing a retro-directive array which uses less power on the low-power mobile side of a wireless link. However, conventional retro-directive arrays, which perform frequency conversion using a mixer and a local oscillator running at twice the RF transmission frequency, are not efficient when implemented in CMOS and can consume a considerable amount of power.
Moreover, on the console (base station) side of the link, tracking circuitry typically alternates between transmitting and listening to the echo, which means that the circuitry needs to rapidly switch between the transmitter and the receiver. However, it is a challenging task to build a decent switch for these high frequencies, with high isolation, low attenuation and high speed.